A novel high-throughput method was established for rapid screening of a large numbers of Aspergillus fumigatus (A. fumigatus) mutants with high chitosanase production under acidic culture condition by exploiting the fact that iodine can be used as the indicator to stain chitosan but is ineffective for chitooligosaccharides. The mutant population was generated by irradiating A. fumigatus CICC 2434 with Co(60)-γ rays. Mutants were cultured on acidic plates containing colloidal chitosan and preliminary screened according to diameter of haloes formed around colonies. Then, chitosanase production of the isolates were verified by dinitrosalicylic acid assay. Lastly, molecular masses on enzymolysis products of isolated mutants were rapidly compared by aniline blue plate assay. Using this method, the mutant strain Co-8 was selected, which had chitosanase activity of 24.87 U/mL (increased by 369.2 % as compared to that of its parental strain).Taking together, the method is easy, efficient and particularly suited to rapid screen acidophilic fungal strains with high chitosanase-production.
Keywords: Aspergillus fumigatus; Chitooligosaccharides; Chitosanase; High-throughput method.